Joomla site gives error for some functionality. It's related with trying to open/read/close folder tree with PHP functions.

Warning: opendir(/var/www/clients/client0/web4/web): failed to open dir: Permission denied in /var/www/clients/client0/web4/web/components/com_component/elements/directories.php on line 102
Warning: readdir(): supplied argument is not a valid Directory resource in /var/www/clients/client0/web4/web/components/com_component/elements/directories.php on line 103
Warning: closedir(): supplied argument is not a valid Directory resource in /var/www/clients/client0/web4/web/components/com_component/elements/directories.php on line 129

if I set web folder 0755 it works without errors and problems
it's sad that IPSConfig changes all web folders to 0710.
What can I do?

Your problem is that you use the wrong php mode. For a website that run a cms system which accesses the filesystem you should always use php-fastcgi plus suexec and not mod-php, so that the php scripts run under the user of the website and not the apache user. Using mod-php with joomla is also a security risk, as its easy for a hacker to infect all your sites when one joomla system is hacked and all sites run under the apache user instead of the website user.